The present invention relates to a hologram and a method of and apparatus for producing the same. Here, it should be noted that the term "produce" as used in the present invention includes "duplicate".
More specifically, the present invention relates to a hologram produced by applying laser light split into two beams to a recording unit including a photosensitive material film placed in close contact with an anti-reflection coated glass or an ND glass or an anti-reflection coated ND glass through an optical contacting liquid, and also relates to a method of producing the hologram.
A hologram original plate has heretofore been duplicated by applying a laser beam to the hologram original plate placed in close contact with a photosensitive material so that diffracted light from the original plate and the incident light interfere with each other in the photosensitive material, thereby recording a hologram image of the original plate in the photosensitive material. In this process, in order to prevent the disorder of the image due to the back reflection component, an optical contacting liquid that is substantially equal to the original plate in refractive index is interposed between the original plate and the photosensitive material, thereby enhancing the adhesion and preventing back reflection during the duplication of the hologram image.
Incidentally, the optical contacting liquid, which is interposed between the glass and the photosensitive material film, is difficult to apply with a uniform thickness because of fluidity, vibration, etc. In particular, when a large amount of contacting liquid is applied, it is likely to take a long time from the application of the liquid to the settlement of its flow, which interferes with the production of a hologram. In addition, even if production or duplication of a hologram is carried out in a clean room, it is impossible to completely eliminate foreign substances (dust) of the order of 10 .mu.m in diameter which are carried in from the outside when the operator enters the room, or when the materials are fed in, and attached to the film and/or the glass. Such foreign substances undesirably lift the film, resulting in regions where the hologram cannot be recorded due to the flow of the optical contacting liquid around the foreign substances. In addition, since the film is pressed by the foreign substances, the hologram produced or made by duplication is attended with a large number of defects (depression-shaped defects) with which a reconstructed image of the hologram looks as if there were depressions of the order of several hundred .mu.m to several mm in diameter.